Fixed rail transportation systems that include one or more a rail vehicles traveling over spaced apart rails of a railway track have been an efficient way of moving cargo and people from one geographical location to another. In densely populated countries and countries having a unimproved road transportation systems, rail vehicles may be the primary means for moving people and cargo. Accordingly, there are probably millions of miles of railroad track throughout the world that need to be maintained to provide safe rail transportation. These railroad tracks need to be routinely inspected to identify problems that may be indicative of incipient track failures. Such track failures may occur as a result of soil and ballast displacement, deterioration of ties supporting the rails, and/or loosening of rail attachment members that may result in track misalignment.
Accordingly, there is a continuing need to improve railway track inspection means. In particular, it is important to ensure that a distance between rails of a railway track, or the rail gage of the track, remain within predetermined ranges such as may be specified by FRA requirements. The gage of a pair of rails is defined by the FRA as the distance between the rails measured at a point five eights of an inch below a top surface of the rail head. Standard U.S. rail gage is specified by the FRA as 56.5 inches. For a U.S. standard gage track, the gage cannot be permitted to spread to more than one inch and a quarter from the U.S. standard gage distance of 56.5 inches.
The most primitive technique for track inspection is to perform a visual inspection of the track to assess track condition. Such an inspection typically involves track inspection personnel walking along or riding adjacent to a track to look for potential track anomalies indicative of potential track failure. This technique may involve the use of various mechanical measuring devices designed to assist the inspection personnel in making track measurements, such as manually measuring a rail gage of the track. However, these manual techniques are time consuming and labor intensive.
Various mechanical rail gage measurement systems have been proposed, but such systems may be susceptible to foreign debris on the rails and still may be too time consuming and may require auxiliary equipment to operate the measurement system. More recently, optical and electromagnetic methods have been proposed to measure rail alignment. Such systems typically rely on sophisticated and expensive electronic hardware for determining rail alignment.